Variable diameter rigid centralizer

Abstract

The application discloses a variable-diameter rigid centralizer belonging to the technical field of oil and gas well engineering. The variable-diameter rigid centralizer comprises a casing, a linkage assembly, an upper fixing frame assembly, a centralizing piece assembly, a lower fixing frame assembly and a vane locking assembly. The variable-diameter centralizer is assembled on a casing string and is lowered to a preset position in a well during cementing operation of a shale gas horizontal well. The vane locking assembly is unlocked, the casing is rotated, and a certain centralizing piece in the centralizing piece assembly rotates relative to the casing under the friction between the centralizing piece and the well wall, the centralizing vane is slowly opened, and each centralizing piece is linked through the linkage assembly to be opened together, thereby realizing the centralizing effect on the casing string. The application can realize casing centering without changing the traditional cementing process, facilitates the casing to be lowered into the well, shortens the casing lowering time, improves the cementing quality of the oil and gas well and increases the economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas well engineering, and particularly relates to a variable-diameter rigid centralizer. BACKGROUND

[0002] In the oil and gas well exploitation engineering, well cementation is one of the key links. The casing centralizer can reduce the casing eccentricity, reduce the bending degree of the casing in the well, can obviously improve the casing centralization, effectively prevent the channeling of the cement slurry, reduce the contact area of the casing and the well wall, can effectively reduce the casing downhole risk and significantly improve the well cementation quality. The traditional rigid centralizer has a large outer diameter, and the outer diameter is not variable. When the casing is lowered into the well, the casing will be rubbed with the well wall, and the lowering is difficult. Especially in the process of cementing the shale gas horizontal well, the elastic centralizer bow piece is easy to compress, the centralizing force is small, the elastic piece is continuously rubbed with the well wall in the process of lowering into the well, the elastic piece is easy to wear, and the supporting capacity is insufficient, and the rigid centralizer is often used.

[0003] Based on the problems existing in the process of lowering the traditional rigid centralizer into the well, a variable-diameter rigid centralizer is designed without changing the traditional well cementation process, which has important practical significance for reducing the well cementation cost and improving the well cementation quality. SUMMARY

[0004] The present application aims to provide a variable-diameter rigid centralizer, which is characterized by comprising a casing, a linkage assembly, an upper fixed frame assembly, a centralizing piece assembly, a lower fixed frame assembly and a blade locking assembly.

[0005] The upper fixed frame assembly comprises an upper outer fixed ring and an upper inner fixed ring; the lower fixed frame assembly comprises a lower outer fixed ring and a lower inner fixed ring; the upper outer fixed ring, the upper inner fixed ring, the lower outer fixed ring and the lower inner fixed ring are fixed on the casing through screws.

[0006] The centralizing piece assembly comprises six identical centralizing blades, and the blade shaft of the centralizing blade is fixed between the rotating holes formed by the upper outer fixed ring and the upper inner fixed ring and the lower outer fixed ring and the lower inner fixed ring.

[0007] The linkage assembly comprises a transmission part and an anti-reverse part; the transmission part comprises a sealing shell, a connecting bearing, a connecting seat, a linkage pinion and a linkage gear; the inner ring of the connecting bearing is mounted on the sleeve, the lower end surface of the outer ring of the connecting bearing is fixedly connected with the connecting seat by screws; the lower surface of the connecting seat is fixedly connected with the upper surface of the linkage gear by screws, and the upper surface of the connecting seat is fixedly connected with the lower surface of the outer ring of the connecting bearing by screws; the linkage pinion is connected with the blade shaft at the upper end of the centralizing blade by a key; the linkage gear is fixedly connected with the outer ring of the connecting bearing through the connecting seat; the anti-reverse part comprises a pawl spring, a pawl, an upper sleeve, a ratchet and a lower sleeve; the ratchet is fixedly connected with the blade shaft; the pawl is mounted on the pawl mounting column of the upper inner fixed ring, and the pawl is fixed between the upper sleeve and the lower sleeve; one end of the pawl spring is connected with the mounting column on the upper end surface of the pawl, and the other end of the pawl spring is connected with the spring mounting column on the upper inner fixed ring.

[0008] The blade locking assembly is used for locking the centralizing blade, so as to prevent the centralizing blade from being opened when the sleeve is lowered.

[0009] The blade locking assembly comprises a first socket, a traction ring and a rotating seat; the lower end of the first socket is connected with the traction ring through a clamping groove, the pin portion of the upper end surface of the first socket is inserted into the hole of the centralizing blade through the hole on the lower outer fixed ring; the rotating seat is fixedly connected with the sleeve by screws; the traction ring is connected with the rotating seat by threads.

[0010] The blade locking assembly comprises a second socket, a catch spring, a catch and a sliding seat; the upper end of the second socket is inserted into the hole in the lower end surface of the centralizing blade, the second socket is clamped on the sliding seat through the catch and the catch spring, so that the second socket slides on the sliding seat in one direction; the catch is distributed around the inside of the second socket, and the catch moves transversely in the second socket through the catch spring; the sliding seat is fixedly connected with the sleeve by screws.

[0011] The blade locking assembly is composed of a pin, and the pin is mounted in the hole in the lower end surface of the centralizing blade.

[0012] A use method of a variable-diameter rigid centralizer, characterized in that the method comprises the following steps:

[0013] Step A1, lowering the sleeve to a designated position in the well;

[0014] Step A2, rotating the sleeve, the protrusions on the surface of the traction ring generate friction with the well wall, the traction ring rotates relative to the rotating seat, the first socket moves downward, the pin shaft at the upper end of the first socket is separated from the hole in the lower end surface of the blade and the hole in the lower inner fixed ring, the blade locking assembly is unlocked, and the centralizing blade assembly is opened;

[0015] Step A3, continue to rotate the casing, the protrusions on the outer surface of the centralizer blades generate friction with the well wall, the casing rotates relative to the centralizer blades, when the individual centralizer blades are in full contact with the well wall, the individual centralizer blades rotate relative to the casing; the linkage pinions rotate under the action of the linkage assembly, thereby driving the linkage gear to rotate, the linkage pinions meshing with the linkage gear produce linkage, and each centralizer blade is opened;

[0016] Step A4, when each centralizer blade is opened to a size suitable for the borehole, the pawl and the ratchet wheel enable the blade shaft to rotate in one direction, the centralizer blades are locked, and the casing centralization work is completed.

[0017] A method for using a variable-diameter rigid centralizer, characterized in that it comprises the following steps:

[0018] Step B1, lower the casing to a designated position downhole;

[0019] Step B2, pull the casing, the second socket slides relative to the sliding seat in one direction, the protrusions on the outer end surface of the second socket generate friction with the well wall, thereby generating axial relative sliding with the casing, the shaft end on the upper part of the second socket is pulled out of the centralizer blade, the blade locking assembly is unlocked, and the centralizer blade assembly is opened;

[0020] Step B3, continue to rotate the casing, the protrusions on the outer surface of the centralizer blades generate friction with the well wall, the casing rotates relative to the centralizer blades, when the individual centralizer blades are in full contact with the well wall, the individual centralizer blades rotate relative to the casing; the linkage pinions rotate under the action of the linkage assembly, thereby driving the linkage gear to rotate, the linkage pinions meshing with the linkage gear produce linkage, and each centralizer blade is opened;

[0021] Step B4, when each centralizer blade is opened to a size suitable for the borehole, the pawl and the ratchet wheel enable the blade shaft to rotate in one direction, the centralizer blades are locked, and the casing centralization work is completed.

[0022] A method for using a variable-diameter rigid centralizer, characterized in that it comprises the following steps:

[0023] Step C1, lower the casing to a designated position downhole;

[0024] Step C2, rotate the casing, the protrusions on the centralizer blades generate friction with the well wall, the pins are subjected to frictional shear force, when the shear stress on the pins exceeds the ultimate stress, the pins are sheared off, the blade locking assembly is unlocked, and the centralizer blade assembly is opened;

[0025] Step C3, continue to rotate the sleeve, the friction force between the protrusions on the outer surface of the centralizer vane and the well wall generates, the sleeve rotates relative to the centralizer vane, when the single centralizer vane is in full contact with the well wall, the single centralizer vane rotates relative to the sleeve, the linkage pinion rotates under the action of the linkage assembly, and in turn drives the linkage gear to rotate, each linkage pinion meshing with the linkage gear is linked, and each centralizer vane is opened;

[0026] Step C4, when each centralizer vane is opened to the size suitable for the borehole, the pawl and the ratchet wheel make the vane shaft rotate in one direction, the centralizer vane is locked, and the centralizing work of the sleeve is completed.

[0027] The beneficial effects of the present application are that:

[0028] 1. When the variable-diameter rigid centralizer of the present application is installed on the sleeve and lowered into the well, the centralizer is in a closed state, effectively solving the problem of large friction force between the traditional rigid centralizer and the well wall when it is lowered into the well, and enabling the sleeve to be smoothly lowered into the well;

[0029] 2. For different sizes of boreholes, the variable-diameter rigid centralizer of the present application rotates different number of turns with the sleeve, the overall outer diameter of the centralizer changes differently, and the centralization of the sleeve in the borehole can be improved;

[0030] 3. The variable-diameter rigid centralizer of the present application adopts modular design, making it more convenient and simple to replace damaged parts, and more convenient to process, manufacture and transport;

[0031] 4. The present application can realize sleeve centralization without changing the traditional cementing process, facilitating the lowering into the well, shortening the sleeve lowering time, improving the quality of oil and gas wells, and increasing economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a three-dimensional axonometric view of the variable-diameter rigid centralizer of the present application;

[0033] Figure 2 is a sectional view of the overall structure of the variable-diameter rigid centralizer of the present application;

[0034] Figure 3 is a sectional view of the linkage assembly;

[0035] Figure 4 is a partial enlarged view of the linkage assembly;

[0036] Figure 5 is a sectional view of the upper fixed frame assembly;

[0037] Figure 6 is a sectional view of the first blade locking assembly;

[0038] Figure 7The structure diagram of the second blade locking assembly;

[0039] Figure 8 The partial enlarged view of the second blade locking assembly;

[0040] Figure 9 The bottom view of the third blade locking assembly;

[0041] Figure 10 The sectional view of the third blade locking assembly;

[0042] Figure 11 The partial enlarged view of the third blade locking assembly;

[0043] Figure 12 The closed state diagram of the variable-diameter rigid centralizer;

[0044] Figure 13 The open state diagram of the variable-diameter rigid centralizer. DETAILED DESCRIPTION

[0045] The present application provides a variable-diameter rigid centralizer, which is further described below in combination with the drawings and specific embodiments.

[0046] Figure 1 、 Figure 2 The three-dimensional axonometric view and the overall structure sectional view of the variable-diameter rigid centralizer; the variable-diameter rigid centralizer comprises a casing 1, a linkage assembly 2, an upper fixing frame assembly 3, a centralizing blade assembly 4, a lower fixing frame assembly 5 and a blade locking assembly 6; during cementing operation, the variable-diameter centralizer is assembled on the casing string and is lowered to a preset position in the well; the blade locking assembly 6 is unlocked, the casing 1 is rotated, and a certain centralizing blade in the centralizing blade assembly 4 rotates relative to the casing under the friction between the well wall and the centralizing blade, the centralizing blade is slowly opened, and each centralizing blade is linked through the linkage assembly 2 to be opened together, thereby realizing the centralizing effect on the casing string;

[0047] The centralizing blade assembly 4 comprises six identical centralizing blades, and the blade shaft of the centralizing blade is fixed between the rotating holes formed by the inner and outer fixing rings of the fixing frame assembly;

[0048] Figure 3 The sectional view of the linkage assembly; Figure 4 The partial enlarged view of the linkage assembly; the linkage assembly 2 comprises a transmission part and an anti-reversing part. The transmission part comprises a linkage large gear 205, a linkage small gear 204, a connecting seat 203, a connecting bearing 202 and a sealing shell 201; the inner ring of the connecting bearing 202 is mounted on the casing, and the outer ring is fixedly connected with the connecting seat 203 through the lower end surface and screws; the lower surface of the connecting seat 203 is fixedly connected with the upper surface of the linkage large gear 205 through screws, and the upper surface is fixedly connected with the lower surface of the outer ring of the connecting bearing 202 through screws;

[0049] The linkage pinion 204 is connected with the central shaft of the centralizer blades by a key. The linkage gear 205 is fixed with the connecting bearing 202 through the connecting seat 203. The transmission part ensures that all the centralizer blades are opened at the same time. The anti-reverse part includes a ratchet wheel 209, a pawl 207, a pawl spring 206, an upper sleeve 208 and a lower sleeve 210. The ratchet wheel 209 is fixed on the blade shaft. The pawl 207 is installed on the pawl mounting column on the upper inner fixing ring 302, and the pawl is fixed between the upper sleeve 208 and the lower sleeve 210. The pawl spring 206 is connected to the upper end surface of the pawl 207 through one end of the mounting column, and is connected to the spring mounting column on the upper inner fixing ring 302 through the other end. The anti-reverse part ensures that the blades are opened in one direction and prevents the blade shaft from being reversed.

[0050] Figure 5 The sectional view of the upper fixing frame assembly is shown. The upper fixing frame assembly 3 includes an upper outer fixing ring 301 and an upper inner fixing ring 302. The lower fixing frame assembly 5 includes a lower outer fixing ring 501 and a lower inner fixing ring 502. The upper outer fixing ring 301, the upper inner fixing ring 302, the lower outer fixing ring 501 and the lower inner fixing ring 502 are fixed on the sleeve through fixing screws.

[0051] The blade locking assembly 6 is used to lock the centralizer blades 401 and prevent the blades from being opened when the sleeve is lowered. Figure 6 The sectional view of the first blade locking assembly is shown. The blade locking assembly 6 scheme one includes a first socket 601, a traction ring 602 and a rotating seat 603. The lower end of the first socket 601 is connected with the traction ring 602 through a clamping groove. The pin part on the upper end surface of the first socket 601 is inserted into the hole on the lower end surface of the centralizer blades 401 through the hole on the lower outer fixing ring 501. The rotating seat 603 is fixed on the sleeve through screws. The traction ring 602 is connected with the rotating seat 603 through threads. When the sleeve is rotated, the traction ring 602 generates friction with the well wall and relative rotation with the sleeve 1. The traction ring 602 rotates on the rotating seat and moves up and down, thereby driving the first socket 601 to move up and down to lock and unlock the centralizer blade assembly.

[0052] Figure 7 、 Figure 8Fig. 6 is a structure diagram and a partial enlarged view of the second blade locking assembly; the second blade locking assembly 6 includes a second socket 701, a latch spring 702, a latch 703, and a sliding seat 704; the upper end of the second socket 701 is inserted into the hole in the lower end surface of the centralizer blade 401, and the socket is clamped on the sliding seat 704 through the latch 703 and the latch spring 702; the second socket 701 can only slide in one direction on the sliding seat 704, facilitating the unlocking of the centralizer blade 401; the latch 703 is installed around the inside of the second socket 701, and the latch 703 moves horizontally in the second socket 701 through the latch spring 702; the sliding seat 704 is fixed to the casing 1 by a screw. When the casing is lowered to a designated position in the well, the casing is pulled, the protrusions on the outer end surface of the second socket 701 rub against the well wall, the second socket 701 and the casing 1 slide axially relative to each other, and the shaft on the upper part of the second socket 701 is pulled out of the centralizer blade 401, thereby completing the unlocking of the centralizer blade.

[0053] Figure 9 、 Figure 10 、 Figure 11 Fig. 7 is a bottom view, a sectional view, and a partial enlarged view of the third blade locking assembly; the third blade locking assembly 6 is composed of a pin 801, which is installed in the hole in the lower end surface of the centralizer blade 401; when the casing is lowered to a designated position in the well, the casing 1 is rotated, the protrusions on the centralizer blade 401 rub against the well wall, the pin 801 is subjected to frictional shear force, and when the shear stress acting on the pin 801 exceeds the ultimate stress, the pin 801 is sheared off, the third blade locking assembly 6 is unlocked, and the centralizer blade 401 is opened.

[0054] Figure 12 、 Figure 13 Fig. 8 is a closed state diagram and an open state diagram of the variable-diameter rigid centralizer; this embodiment provides three methods for using the variable-diameter rigid centralizer, which include the following steps:

[0055] Because the blade locking assembly 6 provides three different unlocking methods, the second step of opening the centralizer is different, and the three methods are described below:

[0056] Method 1:

[0057] Step 1: Lower the casing 1, on which the variable-diameter rigid centralizer is installed, to a designated position in the well.

[0058] Step 2: Rotate the casing 1; the traction ring 602 in the blade locking assembly 6 is subjected to friction between the many protrusions on its surface and the well wall, the traction ring 602 rotates relative to the rotating seat 603, the first socket 601 moves downward, the pin shaft on the upper end of the first socket 601 is pulled out of the hole in the lower end surface of the blade and the hole in the lower inner fixing ring, the blade locking assembly 6 is unlocked at this time, and the centralizer blade assembly 4 can be opened.

[0059] Step 3, continue to rotate the casing 1, due to the protrusions on the outer surface of the centralizer blades 401, the friction between the centralizer blades 401 and the well wall, under the action of friction, the casing 1 relative to the centralizer blades 401 produces rotational motion. Due to the complex environment in the well, when a single centralizer blade is in full contact with the well wall, the single centralizer blade rotates relative to the casing 1. Under the action of the linkage assembly 2, the linkage pinion 204 installed on the blade shaft rotates, the linkage pinion 204 drives the linkage gear 205 to rotate, thereby the linkage of each linkage pinion meshing with the linkage gear 205 is produced, so that each centralizer blade is opened.

[0060] Scheme two:

[0061] Step 1, install the casing 1 with variable diameter rigid centralizer into the designated position in the well;

[0062] Step 2, pull the casing 1, the second socket 701 in the blade locking assembly 6 slides relative to the sliding seat 704 installed therein, and the plurality of locking pins 703 are installed around the inside of the second socket 701. Due to the engagement mode of the locking pins 703 and the sliding seat 704, only one-way sliding of the second socket 701 relative to the sliding seat 704 is allowed, so that the blade locking assembly 6 cannot lock the centralizer blades 401 again, and the situation that the centralizer cannot be opened in the well does not occur.

[0063] Step 3, continue to rotate the casing 1, due to the protrusions on the outer surface of the centralizer blades 401, the friction between the centralizer blades 401 and the well wall, under the action of friction, the casing 1 relative to the centralizer blades 401 produces rotational motion. Due to the complex environment in the well, when a single centralizer blade is in full contact with the well wall, the single centralizer blade rotates relative to the casing 1. Under the action of the linkage assembly 2, the linkage pinion 204 installed on the blade shaft rotates, the linkage pinion 204 drives the linkage gear 205 to rotate, thereby the linkage of each linkage pinion meshing with the linkage gear 205 is produced, so that each centralizer blade is opened.

[0064] Scheme three:

[0065] Step 1, install the casing 1 with variable diameter rigid centralizer into the designated position in the well;

[0066] Step 2, rotate the casing 1, the pin 801 in the blade locking assembly 6 is installed in the hole at the lower end surface of the centralizer blade 401, the protrusions on the centralizer blade 401 generate friction with the well wall, the pin 801 is subjected to friction shear force, when the shear stress of the pin 801 exceeds the ultimate stress, the pin 801 is sheared off, and the blade locking assembly 6 is unlocked.

[0067] Step 3, continue to rotate the casing 1, due to the protrusions on the outer surface of the centralizer blades 401, the centralizer blades 401 and the well wall produce friction, under the action of friction, the casing 1 relative to the centralizer blades 401 produce rotary motion. Due to the complex environment in the well, when a single centralizer blade is in full contact with the well wall, the single centralizer blade rotates relative to the casing 1. Under the action of the linkage assembly 2, the linkage pinion 204 installed on the blade shaft produces rotation, the linkage pinion 204 drives the linkage gear 205 to rotate, thereby the linkage of each linkage pinion meshing with the linkage gear 205 makes each centralizer blade open.

[0068] When each centralizer blade 401 is opened to the size suitable for the borehole, due to the full contact of the centralizer blades 401 with the well wall, the ratchet 209 pawl 207 in the linkage assembly 2 can only make the blade shaft rotate in one direction, the centralizer blades 401 are locked at this time, the centralizer is opened, and the casing 1 centralizing work is completed.

[0069] The variable-diameter rigid centralizer of the application adopts modular design, and it is more convenient and simple to replace damaged parts, and its processing, manufacturing and transportation are more convenient; on the basis of not changing the traditional cementing process, the casing can be centered, which is convenient for lowering into the well, shortens the casing lowering time, improves the quality of oil and gas well cementing, and increases the economic benefit.

Claims

1. A variable diameter rigid centralizer, comprising: The casing (1), the linkage assembly (2), the upper fixing frame assembly (3), the centralizer assembly (4), the lower fixing frame assembly (5) and the blade locking assembly (6) are included. The upper fixing frame assembly (3) includes an upper outer fixing ring (301) and an upper inner fixing ring (302), and the lower fixing frame assembly (5) includes a lower outer fixing ring (501) and a lower inner fixing ring (502); the upper outer fixing ring (301), the upper inner fixing ring (302), the lower outer fixing ring (501) and the lower inner fixing ring (502) are fixed on the casing (1) by screws. The centralizer assembly (4) includes six identical centralizer blades (401), and the blade shaft of the centralizer blade (401) is fixed between the rotating holes formed by the upper outer fixing ring (301) and the upper inner fixing ring (302) and the lower outer fixing ring (501) and the lower inner fixing ring (502). The linkage assembly (2) includes a transmission part and an anti-reverse part; the transmission part includes a sealing shell (201), a connecting bearing (202), a connecting seat (203), a linkage pinion (204) and a linkage gear (205); the inner ring of the connecting bearing (202) is installed on the casing (1), and the lower end surface of the outer ring of the connecting bearing (202) is fixedly connected with the connecting seat (203) by screws; the lower surface of the connecting seat (203) is fixedly connected with the upper surface of the linkage gear (205) by screws, and the upper surface of the connecting seat (203) is fixedly connected with the lower surface of the outer ring of the connecting bearing (202) by screws; the linkage pinion (204) is connected with the blade shaft at the upper end of the centralizer blade (401) by a key; the linkage gear (205) is fixedly connected with the outer ring of the connecting bearing (202) through the connecting seat (203); the anti-reverse part includes a pawl spring (206), a pawl (207), an upper sleeve (208), a ratchet wheel (209) and a lower sleeve (210); the ratchet wheel (209) is fixedly connected with the blade shaft; the pawl (207) is installed on the pawl installation column of the upper inner fixing ring (302), and the pawl (207) is fixed between the upper sleeve (208) and the lower sleeve (210); one end of the pawl spring (206) is connected with the installation column on the upper end surface of the pawl (207), and the other end is connected with the spring installation column on the upper inner fixing ring (302); The blade locking assembly (6) is used for locking the centralizer blade to prevent the centralizer blade (401) from being opened when the casing (1) is lowered.

2. The variable gauge rigid centralizer of claim 1, wherein, The blade locking assembly (6) includes a first socket (601), a traction ring (602) and a rotating seat (603); the lower end of the first socket (601) is connected with the traction ring (602) through a clamping groove, and the pin portion of the upper end surface of the first socket (601) is inserted into the hole of the centralizer blade (401) through the hole in the lower outer fixing ring (501); the rotating seat (603) is fixedly connected with the casing (1) by screws; the traction ring (602) is connected with the rotating seat (603) by threads.

3. The variable gauge rigid centralizer of claim 1, wherein, The blade locking assembly (6) comprises a second socket (701), a catch spring (702), a catch (703), and a sliding seat (704). The upper end of the second socket (701) is inserted into the hole in the lower end surface of the centralizer blade (401). The second socket (701) is clamped on the sliding seat (704) by the catch (703) and the catch spring (702), so that the second socket (701) slides on the sliding seat (704) in one direction. The catch (703) is distributed around the inside of the second socket (701), and the catch (703) moves laterally in the second socket (701) by the catch spring (702). The sliding seat (704) is fixed to the casing (1) by a screw.

4. The variable gauge rigid centralizer of claim 1, wherein, The blade locking assembly (6) is composed of a pin (801), which is installed in the hole in the lower end surface of the centralizer blade (401).

5. A method of using the variable diameter rigid centralizer of claim 2, wherein, The method comprises the following steps: Step A1, lower the casing (1) to the designated position in the well; Step A2, rotate the casing (1), so that the protrusions on the surface of the traction ring (602) generate friction with the well wall, the traction ring (602) rotates relative to the rotating seat (603), the first socket (601) moves downward, the pin shaft at the upper end of the first socket (601) is pulled out of the hole in the lower end surface of the blade and the hole in the lower inner fixing ring (502), the blade locking assembly (6) is unlocked, and the centralizer assembly (4) is opened; Step A3, continue to rotate the casing (1), so that the protrusions on the outer surface of the centralizer blade (401) generate friction with the well wall, the casing (1) rotates relative to the centralizer blade (401), and when a single centralizer blade (401) is in full contact with the well wall, the single centralizer blade (401) rotates relative to the casing (1); the linkage pinion (204) rotates under the action of the linkage assembly (2), thereby driving the linkage gear (205) to rotate, and the linkage pinions (204) meshing with the linkage gear (205) are linked, and each centralizer blade (401) is opened; Step A4, when each centralizer blade (401) is opened to a size suitable for the borehole, the pawl (207) and the ratchet wheel (209) allow the blade shaft to rotate in one direction, the centralizer blade (401) is locked, and the centralizing work of the casing (1) is completed.

6. A method of using the variable diameter rigid centralizer of claim 3, wherein, The method comprises the following steps: Step B1, lower the casing (1) to the designated position in the well; Step B2, pull the casing (1), so that the second socket (701) slides in one direction relative to the sliding seat (704), the protrusions on the outer end surface of the second socket (701) generate friction with the well wall, thereby generating axial relative sliding with the casing (1), the shaft end at the upper part of the second socket (701) is pulled out of the centralizer blade (401), the blade locking assembly (6) is unlocked, and the centralizer assembly (4) is opened; Step B3, continue to rotate the casing (1), the protrusions on the outer surface of the centralizer blades (401) generate friction with the well wall, the casing (1) rotates relative to the centralizer blades (401), when a single centralizer blade (401) is in full contact with the well wall, the single centralizer blade (401) rotates relative to the casing (1); the linkage pinions (204) rotate under the action of the linkage assembly (2), and in turn drive the linkage gear wheels (205) to rotate, the linkage pinions (204) meshing with the linkage gear wheels (205) are linked, and each centralizer blade (401) is opened; Step B4, when each centralizer blade (401) is opened to a size suitable for the wellbore, the pawl (207) and the ratchet wheel (209) allow the blade shaft to rotate in one direction, the centralizer blade (401) is locked, and the centralizing of the casing (1) is completed.

7. A method of using the variable diameter rigid centralizer of claim 4, wherein, The method comprises the following steps: Step C1, lower the casing (1) to a designated position downhole; Step C2, rotate the casing (1), the protrusions on the centralizer blades (401) generate friction with the well wall, the pins (801) are subjected to shear friction, when the shear stress on the pins (801) exceeds the ultimate stress, the pins (801) are sheared off, the blade locking assembly (6) is unlocked, and the centralizer blade assembly (4) is opened; Step C3, continue to rotate the casing (1), the protrusions on the outer surface of the centralizer blades (401) generate friction with the well wall, the casing (1) rotates relative to the centralizer blades (401), when a single centralizer blade (401) is in full contact with the well wall, the single centralizer blade (401) rotates relative to the casing (1), the linkage pinions (204) rotate under the action of the linkage assembly (2), and in turn drive the linkage gear wheels (205) to rotate, the linkage pinions (204) meshing with the linkage gear wheels (205) are linked, and each centralizer blade (401) is opened; Step C4, when each centralizer blade (401) is opened to a size suitable for the wellbore, the pawl (207) and the ratchet wheel (209) allow the blade shaft to rotate in one direction, the centralizer blade (401) is locked, and the centralizing of the casing (1) is completed.

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